This invention relates to a steam generator for use in conjunction with a device, such as a medical device steam sterilizer, that requires a supply of pressurized steam. The generator and the device are integrated into a single unit so that the generator supplies steam directly to the portion of the device requiring the steam. When integrated with a steam sterilizer the generator supplies steam directly to the sterilizer jacket or chamber.
Certain types of devices, such as steam sterilizers, require pressurized steam for their operation. Some of these devices create steam by boiling water inside a chamber within the device, such as a sterilizer chamber, using an immersion heater. An immersion heater essentially is a large heating element usually located over the bottom surface of the chamber. An immersion heater has several disadvantages, however.
An immersion heater can be a relatively large piece of equipment. It works best when its wattage can be spread out over a large heating element surface area. This keeps the watt density low and extends the life of the heating element. This large heating element surface area, however, requires a lot of space and greatly increases the size of the steam generator and of the overall device when the generator is within the device.
An immersion heater also must have its heating element completely immersed in water. To remain immersed the large heating element thus requires a large volume of water--a much larger volume of water than the sterilizer needs to complete a sterilization cycle. This large volume of water must be disposed of at the end of each pressure pulse during a sterilizaton cycle, including at the end the entire sterilization cycle. Unified plumbing codes require that the water be cooled in a heat exchanger or mixed with cooling water before disposing it down a building drain. Also, a large volume of heated water requires a proportionately large amount of cooling water. Thus the disposal process consumes a substantial amount of water. Furthermore, due to the significant amount of chamber water required, an immersion heater used with a sterilizer increases the total length of the sterilization cycle because of the time required at the start of the cycle to bring the large volume of sterilizer chamber water up to boiling temperature to start generating steam.
An immersion heater also is prone to several service and reliability problems. The heater is prone to leaks where the heating element passes through the wall of the sterilizer chamber. The overtemperature protection device for the heater also must be inside the chamber, immersed in water or steam, and, therefore, its connections also must pass through the chamber wall creating additional potential leakage points. In addition, scale or mineral deposits build up on the heating element surface, reducing the heat transfer efficiency and heater life.
In contrast to using an immersion heater within a device, steam may be provided from a stand-alone boiler to the device requiring pressurized steam, such as a steam sterilizer. A stand-alone boiler is more costly than an immersion heater built into a device because it must be purchased as an entirely separate component from the device. In addition, a stand-alone boiler generally uses an immersion heater to produce steam, and, therefore, is prone to the same problems associated with that type of heater. In particular, the stand-alone boiler also requires time-consuming flushing procedures to clear mineral deposits that build up inside the boiler chamber.
The present invention provides a flash steam generator that is integral with a medical device steam sterilizer or other device requiring pressurized steam. Thus, it is less costly than a stand-alone boiler. In addition, in contrast to current steam sterilizers and stand-alone boilers, the steam generator of the present invention does not use an immersion heater to produce steam. The heating mechanism used in the present invention requires substantially less water, which decreases the sterilization cycle time and provides easier and more efficient water disposal. Furthermore, unlike an immersion heater, the heating mechanism of the present invention is not prone to leaks or the build up of scale or mineral deposits.